Liquid crystal display devices have advantages such as light weight, thinness, and low power consumption, and are utilized not only for large-size television sets but also as small-sized display devices, e.g., display sections of mobile phones.
A liquid crystal display device includes a liquid crystal display panel, a backlight device, circuitry and a power supply for supplying various electrical signals to the liquid crystal display panel, and a housing which accommodates these. The liquid crystal display panel has a displaying region in which a plurality of pixels are arrayed, and a frame region around it.
The displaying region (active area) of a generic liquid crystal display device includes pixel electrodes, thin film transistors (TFTs), and the like provided therein, in which images, videos, or the like are displayed. In the frame region are provided: a sealing portion at which substrates are attached together so that a liquid crystal material is sealed in between the substrates; connection lines connected to the gate electrodes and source electrodes of the TFTs; terminals for connection with external driving circuits which input signal/scanning voltages; and so on. In the present specification, any region in which connection lines to the gate electrodes and source electrodes of TFTs, terminals for connection with external driving circuits which input signal/scanning voltages, and the like are located may be referred to as a connection region. In order to prevent deteriorations in display quality at the outer periphery of the active area due to leakage of light from the backlight, disorderly alignment of liquid crystal molecules, and so on, a black mask (light-shielding member) is usually provided in the frame region. Thus, the frame region is a region not contributing to displaying (invalid displaying portion). While liquid crystal display devices are becoming narrower and narrower in their frames each year, it is difficult to eliminate the frame region.
Now, a frame region 81a of a generic liquid crystal display panel (e.g., a TN (Twisted Nematic) type liquid crystal panel) 500 will be described with reference to FIG. 9(a) and FIG. 9(b). FIG. 9(a) is a schematic plan view of the liquid crystal display panel 500, and FIG. 9(b) is a schematic cross-sectional view of an a portion shown in FIG. 9(a).
The liquid crystal display panel 500 has a displaying region 81 and a frame region 81a located at the periphery of the displaying region 81. A plurality of pixel electrodes 4 are formed in the displaying region 81 of the liquid crystal display panel 500. The frame region 81a is a region which does not contribute to displaying. In the frame region 81a of the liquid crystal display panel 500, a sealing portion 99 is formed so as to surround the liquid crystal layer 1. The width Ds of the frame region 81a is expressed as a sum of the width D1 of the sealing portion 99 and the distance D2 between the sealing portion 99 and a pixel electrode 4 which is adjacent to the sealing portion 99 (where the distance D2 may be about 1.5 mm, for example). The sealing portion 99 is formed by using a dispenser apparatus, a screen printer, or the like to apply a sealant on a substrate so as to constitute a predetermined pattern, and, after this is attached to the other substrate, curing the sealant. The final width D1 of the sealing portion 99 is about 1 mm or more.
On the other hand, Patent Document 1 discloses a liquid crystal display panel having a polymer dispersed liquid crystal (PDLC) layer in which a curable vinyl compound is used. Patent Document 2 states that forming a polymer dispersed liquid crystal layer from a curable vinyl compound provides an effect of adhesively bonding the pair of substrates, without even forming the sealing portion 99 which would belong to the liquid crystal display panel 500.